Miniaturization of optical, electro-optical, and optoelectronic components and modules is reaching a stage where complex optical, electro-optical, and optoelectronic functionalities may be realized on a single semiconductor chip. For example, a semiconductor chip may be patterned with so-called “photonic integrated circuits” including optical waveguides and other micro-optical structures. The photonic integrated circuits may be used for modulation, demodulation, detection, and wavelength separation of optical signals, making them attractive for optical communications systems. The proliferation of microelectronics technology has a potential for integration of photonic chips with electronic circuitry.
Recently, photonic chips have been increasingly used for generation, modulation, demodulation, and reception of light signals in telecommunications networks. Functions such as transmission, reception, and modulation of light have been realized on one or several photonic chips. Despite the progress of optical integration technologies on photonic chips, the task of in-coupling and out-coupling of light between a photonic chip and outside environment remains a significant challenge. The multitude of densely spaced optical inputs and outputs may render coupling of optical fibers difficult.
Several optical interface standards have been developed to provide dense multiport optical connector components. One example of such a standard is a “parallel singlemode 4” (PSM4) optical interface standard, which uses connectorized single mode fiber ribbons to support reaches of at least 500 meters. The fiber ribbons may be connected to optoelectronic devices and modules via arrayed connectors such as, for example, Multi-Fiber Push-On (MPO) connectors. Another example is Coarse Wavelength Division Multiplexer (CWDM) optical interface standard, which uses two single mode fibers to carry four multiplexed wavelengths per fiber. In the CWDM standard, one optical fiber carries upstream optical signals, and the second optical fiber carries downstream optical signals.
Regardless of which multiport optical connector is used to couple an optical device to a fiber array, a task remains of optical coupling of the photonic chip to the optical connector inside the device. Typically, a fiber array is coupled to an edge of a photonic chip where the waveguides of the chip terminate. A more recent optical coupling technology uses so-called vertical coupling gratings, which enable a fiber array to be coupled to a planar surface of the chip at a nearly straight angle.
One potential drawback of fiber array coupling is that a relatively large space, in comparison with the photonic chip size, is required to accommodate the minimal fiber bend radius of the optical fiber. When a side coupling is used, the resulting optomechanical assembly tends to be long due to the requirement to stress relieve optical fibers extending within a package between the photonic chip and a multi-fiber connector. When a vertical coupling is used, the optical fibers extend upwards, resulting in a package height increase.